I think this will be final wallpaper, simply because Apple have paid for the image from a photographer, like they did with the final iOS 8 wallpaper.
Also, like the final iOS 8 wallpaper, they've made some adjustments to it. They removed what appears to be a head from the end of the wave on this one and on iOS 8's stock wallpaper they removed a small house from the bottom of the hill.
iOS 8's beta wallpaper last year was just rendered rippled water.
I don't see Apple paying to use someone's photo and editing it, again like they done with the final
iOS 8 wallpaper, to ditch it after the betas.